How to Check Your Charging System Before Winter

Your vehicle’s charging system carries a heavier burden once the winter months roll around. Shorter days mean that the headlights and accessory lights are on more often, and the heating system draws extra current for the blower and seats. Meanwhile, the entire setup is subjected to chilling temperatures, which can expose wiring flaws or issues with the alternator or battery that weren’t apparent in warmer weather.

That last point is the reason it’s important to have your vehicle’s charging system checked before the snowy weather hits. You want to make sure you’re heading into the coldest season of the year in the best possible shape. How can you do this? Let’s take a closer look.

Check Your Battery

One of the easiest things to check in your car’s charging system is the battery. First, consider how old your battery is. If you installed it more than five years ago, chances are it’s on its way out. If you’re not sure when your battery was purchased, you can check the manufacturing date code, which is carved into the top of the unit itself. The letter indicates the month (A = January, B = February, etc.), and the number is the year (4 = 2004, 15 = 2015, etc.). Most batteries are sold within three months of being manufactured.

Second, examine the battery’s appearance. Look for signs of corrosion at the terminals, any wetness on the top, sides, or bottom of the battery, and bulges in the battery casing. Any of these conditions could be an indication that the battery won’t make it through the winter.

Finally, if everything looks good but you still have doubts, you can always take your battery to a local auto parts store or your mechanic to have it load-tested. This will tell you whether its internal cells are still capable of handling a working load.

Verify Your Alternator

Another important part of any healthy car charging system is the alternator, which is the component that actually generates the juice necessary to keep your battery topped up and your vehicle’s systems running smoothly.

Testing your alternator is a very simple process. Using a multimeter, you can measure the voltage across the terminals of your vehicle’s battery while it is idling. (Note that this test assumes you have a healthy battery.) It should read 14.2 volts in normal, pre-winter weather. Revving the engine should cause the voltage reading to change, typically to a value of between 13.5 and 14.5 volts. Anything else—including a steady voltage reading at higher revs—is a potential sign of an undercharging or overcharging issue with your alternator that should be addressed. Turning on your lights and heater will also drop the voltage, but it should always stay above 13 volts.

Starter Draw Is Important, Too

Your vehicle’s starter draws more current from your battery than any other component under the hood. If it’s pulling too much electricity, it can cause problems in winter weather.

Using the same multimeter, have a friend start your car while you measure the voltage across the battery terminals as before. The reading should remain above 10 volts. If it dips lower, or if the starter is sluggish in turning over the engine, you’ll want to verify that the connections between it and the battery are not loose or corroded.

Remember—a healthy charging system will greatly reduce your chances of getting stranded in the dead of winter. It’s worth taking the time to see that it’s problem-free to ensure safe driving year-round.

Check out all the engine electrical products available at, or trust one of our 600 NAPA AUTOPRO shops for car routine maintenance and repairs. For more information on your vehicle’s charging system, chat with an expert at your local NAPA Auto Parts store.

By Benjamin Hunting

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